Function Point Count

\[UFP=EI+EO+EQ+ILF+EIF\]

Variables

UFPunadjusted function points

EIweighted external inputs

EOweighted external outputs

EQweighted external inquiries

ILFweighted internal logical files

EIFweighted external interface files

Description

What is this formula?

Function Point Count measures the functional size of a software system from the user's perspective.

The Unadjusted Function Point (UFP) method estimates software size by counting and weighting five types of functional components.

Unlike source code metrics, function points are independent of programming language and implementation technology.

When to use it

Use this formula when:

- estimating software projects,

- comparing systems built with different technologies,

- evaluating productivity,

- planning development effort,

- estimating maintenance workloads.

Example

Suppose a project contains:

EI = 35

EO = 28

EQ = 12

ILF = 20

EIF = 10

Formula:

UFP = EI + EO + EQ + ILF + EIF

Substitution:

UFP = 35 + 28 + 12 + 20 + 10

UFP = 105

Result:

Unadjusted Function Points = 105

Applications

- Software estimation

- Project planning

- Productivity analysis

- Cost estimation

- Outsourcing contracts

- Software portfolio management

Note

Function Point Analysis is an empirical sizing methodology. In formal IFPUG analysis, each component is assigned complexity-based weights before calculating UFP. Additional adjustment factors may also be applied in some methodologies. The simplified formula presented here assumes that the weighted values of each component are already known.